MXS-1506: Add delayed_retry parameter

By adding a boolean parameter, the feature can be enabled with sensible
default values. Renamed the query_retry parameters and set the defaults to
acceptable values.

Added new parameters to diagnostic output. Also did some minor renaming.

server/modules/routing/readwritesplit/readwritesplit.cc

@@ -338,10 +338,12 @@ void RWSplit::diagnostics(DCB *dcb)
                config().causal_read_timeout.c_str());
     dcb_printf(dcb, "\tmaster_reconnection:       %s\n",
                config().master_reconnection ? "true" : "false");
-    dcb_printf(dcb, "\tquery_retry_timeout:       %lu\n",
+    dcb_printf(dcb, "\tdelayed_retry:        %s\n",
-               config().query_retry_timeout);
+               config().delayed_retry ? "true" : "false");
-    dcb_printf(dcb, "\tquery_retry_interval:       %lu\n",
+    dcb_printf(dcb, "\tdelayed_retry_timeout:       %lu\n",
-               config().query_retry_interval);
+               config().delayed_retry_timeout);
+    dcb_printf(dcb, "\tdelayed_retry_interval:       %lu\n",
+               config().delayed_retry_interval);
 
     dcb_printf(dcb, "\n");
 
@@ -415,10 +417,12 @@ json_t* RWSplit::diagnostics_json() const
                         json_string(config().causal_read_timeout.c_str()));
     json_object_set_new(rval, "master_reconnection",
                         json_boolean(config().master_reconnection));
-    json_object_set_new(rval, "query_retry_timeout",
+    json_object_set_new(rval, "delayed_retry",
-                        json_integer(config().query_retry_timeout));
+                        json_boolean(config().delayed_retry));
-    json_object_set_new(rval, "query_retry_interval",
+    json_object_set_new(rval, "delayed_retry_timeout",
-                        json_integer(config().query_retry_interval));
+                        json_integer(config().delayed_retry_timeout));
+    json_object_set_new(rval, "delayed_retry_interval",
+                        json_integer(config().delayed_retry_interval));
 
     json_object_set_new(rval, "connections", json_integer(stats().n_sessions));
     json_object_set_new(rval, "current_connections", json_integer(service()->stats.n_current));
@@ -498,8 +502,9 @@ MXS_MODULE *MXS_CREATE_MODULE()
             {"enable_causal_read", MXS_MODULE_PARAM_BOOL, "false"},
             {"causal_read_timeout", MXS_MODULE_PARAM_STRING, "0"},
             {"master_reconnection", MXS_MODULE_PARAM_BOOL, "false"},
-            {"query_retry_timeout", MXS_MODULE_PARAM_COUNT, "10"},
+            {"delayed_retry", MXS_MODULE_PARAM_BOOL, "false"},
-            {"query_retry_interval", MXS_MODULE_PARAM_COUNT, "0"},
+            {"delayed_retry_timeout", MXS_MODULE_PARAM_COUNT, "10"},
+            {"delayed_retry_interval", MXS_MODULE_PARAM_COUNT, "1"},
             {MXS_END_MODULE_PARAMS}
         }
     };

server/modules/routing/readwritesplit/readwritesplit.hh

@@ -174,8 +174,9 @@ struct Config
         enable_causal_read(config_get_bool(params, "enable_causal_read")),
         causal_read_timeout(config_get_string(params, "causal_read_timeout")),
         master_reconnection(config_get_bool(params, "master_reconnection")),
-        query_retry_timeout(config_get_integer(params, "query_retry_timeout")),
+        delayed_retry(config_get_bool(params, "delayed_retry")),
-        query_retry_interval(config_get_integer(params, "query_retry_interval"))
+        delayed_retry_timeout(config_get_integer(params, "delayed_retry_timeout")),
+        delayed_retry_interval(config_get_integer(params, "delayed_retry_interval"))
     {
         if (enable_causal_read)
         {
@@ -203,8 +204,9 @@ struct Config
     bool              enable_causal_read;        /**< Enable causual read */
     std::string       causal_read_timeout;       /**< Timeout, second parameter of function master_wait_gtid */
     bool              master_reconnection;       /**< Allow changes in master server */
-    uint64_t          query_retry_timeout;       /**< Time window in which a query can be retried */
+    bool              delayed_retry;           /**< Delay routing if no target found */
-    uint64_t          query_retry_interval;      /**< Time window in which a query can be retried */
+    uint64_t          delayed_retry_timeout;   /**< How long to delay until an error is returned */
+    uint64_t          delayed_retry_interval;  /**< How often to attepmt to route the delayed query */
 };
 
 /**

server/modules/routing/readwritesplit/rwsplit_route_stmt.cc

@@ -241,13 +241,15 @@ bool RWSplitSession::route_single_stmt(GWBUF *querybuf, const RouteInfo& info)
         else if (can_retry_query())
         {
             // Try to route the query again later
-            uint64_t interval = m_config.query_retry_interval;
+            uint64_t interval = m_config.delayed_retry_interval;
             MXS_SESSION* session = m_client->session;
             session_delay_routing(session, router_as_downstream(session),
                                   gwbuf_clone(querybuf), interval);
-            m_retry_duration += interval;
             succp = true;
 
+            // Increment by at least one to prevent infinite delay
+            m_retry_duration += interval > 0 ? interval : 1;
+
             MXS_INFO("Will try to route query again in %lu seconds", interval);
         }
     }

server/modules/routing/readwritesplit/rwsplitsession.hh

@@ -188,8 +188,8 @@ private:
 
     inline bool can_retry_query() const
     {
-        return m_config.query_retry_interval > 0 &&
+        return m_config.delayed_retry &&
-               m_retry_duration < m_config.query_retry_timeout &&
+               m_retry_duration < m_config.delayed_retry_timeout &&
                !session_trx_is_active(m_client->session);
     }